


onii-chan!

by irreversible



Category: Persona 5
Genre: Alternate Universe - Canon Divergence, Anal Fingering, Anal Sex, Bottom Persona 5 Protagonist, Dead Dove: Do Not Eat, Incest, M/M, Overstimulation, Shotacon, Sibling Incest, Size Difference, Size Kink, Top Akechi Goro, consensual but not very sane, heavy underage
Language: English
Status: Completed
Published: 2021-02-14
Updated: 2021-02-14
Packaged: 2021-03-17 17:28:47
Rating: Explicit
Warnings: Underage
Chapters: 1
Words: 2,948
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/29354229
Author URL: https://archiveofourown.org/users/irreversible/pseuds/irreversible
Summary: "Onii-chan,” Ren giggles. “Did you get bigger again?”Goro loves his little brother maybe a little too much. But that's ok because Ren loves him a little too much, too.
Relationships: Akechi Goro/Amamiya Ren, Akechi Goro/Kurusu Akira, Akechi Goro/Persona 5 Protagonist
Comments: 14
Kudos: 78





	onii-chan!

**Author's Note:**

> **you clicked this AND read the tags. akechi is 17, ren is 8, and both are siblings for the purpose of this fanfic. dont ask me how or why. ******
> 
> **  
> **i don't want anyone complaining in the comments, only people who quietly log out of their main to comment that they want more of this akeshu shit. or maybe you are brave and comment on main, who knows??**  
> **
> 
> **  
> **ahh, the wonders of this forbidden world.**  
> **

“Goro,” Ann says, wincing a little. Most likely at what she’s going to say, judging by the hesitant call of his name. “Don’t you think you’re overdoing it a little?”  
  
Goro barely pays her any attention. Ren’s shirt has ridden up while climbing the slide reverse style, flashing teasing bits of soft, pale skin.  
  
Unmarked. Maybe he could finally allow himself to change that. Play it off as insect bites or allergies when somebody catches on.

 _Who would?_  
  
Not that Goro would ever be actually suspected of laying hands on his small, little brother.  
  
“What do you mean?” he asks, more to entertain Ann than himself.  
  
She fidgets a little on her spot on the bench next to him, crossing and uncrossing her legs. Bracelets clink against each other.  
  
"Well. I just recently noticed you keep him on a very tight leash.”

Ann gestures towards the playground, void of any other children as if he’s responsible for it. Goro wonders if bystanders think he and Ann are a couple. Or Siblings?  
  
He snorts at the irony.

"I know the bullying incidents really scared Ren, but not allowing him to play with anyone else is...”  
  
 _What do you even know?_ Goro wants to snarl. Turn and throttle the insolent girl he keeps by his side for convenience purposes only, dig his thumbs into the hollow of her throat and irreversibly press until resistance gives.  
  
Instead, Goro tames the monster by smiling impeccably. “He doesn’t want to,” he explains. His expression turns genuine when he calls for his darling brother. “Ren?”  
  
And like the bright ray of sunshine he is, Ren’s whole expression lights along with the ragged edges of Goro’s world as he snaps his head towards his big brother.  
  
Forgoing the slide completely, Ren jumps down not a second later, eagerly running towards Goro.

All with just the call of his name.  
  
Goro’s heart swells.

“Onii-chan!”  
  
Goro effortlessly catches Ren when the other jumps. He settles him into his lap where Ren slings his short legs around Goro’s waist and hugs Goro’s chest like a koala.  
  
The 8-year old is still so small that Goro has to lean down a little in order to be able to prop his chin on Ren’s head. Or maybe Goro’s just that much taller. Both thoughts make his heart race.  
  
But all that matters is that Ren fits so, so perfectly against him that everything else dulls. Goro can’t even be mad at Ann for questioning him in the first place.  
  
He can barely comprehend this himself, so how should she?

“Tell her, Renren,” Goro speaks into the fluffy crown of feathery black, allowing mild amusement to paint his tone. “Do you want to play with other kids?”  
  
“No!” comes the immediate answer, and pride blooms in Goro’s chest. He leans in to press a kiss to Ren’s temple.  
  
“And why is that?”  
  
“I only need Goro-nii chan, “ Ren murmurs into the fabric of his dress-shirt. Quietly, but oh so insistent and convinced. “The rest are boring and mean.”  
  
“Good kitten,” Goro whispers, tightening his grip around Ren’s waist at the blunt confession.  
  
It’s so small that he can encircle most of it with one hand.  
  
Ren squirms in his lap, already having learned what the words usually entail, but he calms down fast enough and hides himself a little more in Goro’s body, suddenly shy.  
  
How to describe the illicit, forbidden feelings coursing through Goro’s veins in every waking minute? The genuine, but once innocent affection streaked with poisonous desire?  
  
Goro is strong, but with Ren, he’s a but a mere weak human.  
  
“I love onii-chan the most,” he hears Ren mumble, loud enough for Ann to hear.

  
But she doesn’t exist anymore. It’s only Goro and his small, wonderful, perfect little brother, sitting in Goro’s lap where he belongs and fixing all crooked edges and wrong angles in the world.  
  
“That’s right,” Goro croons affectionately , nuzzling Ren’s hair. It’s soft, just like everything else that is Ren.  
  
“I’m the only one you need.”

  
  
"Onii-chan,” Ren giggles. “Did you get bigger again?”  
  
Goro can’t help but buck his hips into Ren’s explorative touch. Ren’s hand just barely fits over and aroundhis cockhead, and the image is setting his stomach ablaze.  
  
“It’s my love for you,” Goro breathlessly laughs.

With the hand that isn’t propping himself up, he brushes some bangs out of Ren’s face.  
  
His little brother makes a thoughtful face before nodding importantly, most likely deciding that what Goro says is right.

It’s not untrue. Goro is 17, and he’ll most likely still grow a little, in height especially. It’s something he’s looking forward to, because him being bigger than Ren in all ways is just right in a primal sort of way.  
  
Though looking at Ren’s small, thin frame, he doubts he'll have much to worry about.  
  
Another hiss escapes him when Ren’s hands slide lower, trying to fit around his girth. Clumsy movements make the wet slide all the more obscene.  
  
“Renren,” Goro calls, because he doesn’t think he can hold back any longer, not when his small, cute brother stares at his cock like it’s either a toy to play with or candy to devour.  
  
He’s never managed to defile that aspect of innocence of him.  
  
"Yes, onii-chan?” Ren asks, large pools of grey peeking up at him.  
  
“You’re really testing your big brother’s patience right now,” Goro grits out, half amused, half impatient.  
  
He’s been hard since Ann left the playground and Goro brought Ren back home. He had Ren sit in his lap on the entire train ride in order to hide the obvious bulge in his pants, a method which was unfortunately not helping his actual problems, especially because Ren kept moving his goddamn little hips.  
  
All friction against his cock was (is) torture.  
  
Ren giggles in response and squeezes a little because beneath that sweet facade he can be a little shit at times. So Goro simply reaches over to pull Ren closer against the length he’s so nonchalantly playing with.

And, god.  
  
Heat ignites in all of his pores.  
  
Goro makes quick work of Ren’s shirt to drag the pads of his fingers over his flat, soft stomach. Calculative.

“It tickles,” Ren complains, squirming. Goro draws lines and stops a bit above his belly button. “What are you doing, onii-chan?”  
  
“Measuring how deep I’ll reach,” Goro answers with a smirk Ren probably can't see at this angle in the dim lighting of their bedroom.  
  
Because his cock is a little more than half the size of Ren’s torso and the knowledge and visual proof does _things_ to him.  
  
It was a tedious process to get Ren accustomed to his size to the point where he could fuck him somewhat regularly and deeply, and even now he’s still convinced that the toilet problems Ren sometimes has are because of him, but it’s a small price to pay to relinquish the unbelievably tight and hot heat of his beloved brother.  
  
Shido’s doctors have seen worse anyway. They're being paid to keep quiet primarily, the skills their profession brings them secondary.  
  
Ren flushes prettily at Goro’s comment, but his squirming resumes, clearly growing restless as well.  
  
“I’ll start, kitten,” Goro murmurs, tugging down Ren’s little shorts.  
  
His little brother makes a face. “Can’t you put it in already? I don’t want to wait every time!”

“Renren, we went over this already,” Goro sighs with mild amusement. “It already hurts a little when I push inside, right?”  
  
Ren reluctantly nods. “But you always make me feel so good after that!”  
  
“Mhm, I know kitten. That’s why we can’t skip this step. It’d hurt a lot more otherwise.”  
  
Ren pouts, but sighs happily when Goro probs at his entrance with a lubed finger. His long eyelashes flutter, and Goro allows himself a moment to admire how pretty his little brother is.  
  
All for him. The only good thing he ever got out of this rotten world.  
  
He can’t help but dip down, catching Ren’s lips with his. His darling brother complies so easily, tilts his head back to meet him, allows Goro to take what he wants with soft mewls.  
  
“Good kitten,” Goro murmurs after he tasted enough of his sweetnes to momentarily disconnect. His finger resumes teasing Ren’s rim, enjoying Ren’s flushed face and bleary eyes.

“That’s the sound I want to hear. You can use me while I work you open.”  
  
“Hmm?”  
  
Goro shallowly thrusts his hips upwards once. Ren seems to get the idea, blinking dazedly before working on the front side of his shorts. Goro groans at the sight - Ren is so unbelievably small against his own cock that the sight makes him feel a little light headed. His cock twitches.  
  
“Onii-chan,” Ren whimpers, winding his arms around Goro’s torso again, successfully trapping not only Goro’s cock between their bodies, but also slotting Ren’s little cocklet against the base of it.  
  
“That’s it,” Goro whispers, using his other hand to spread Ren’s soft cheeks wider, feeling his tiny sack. “Chase your own pleasure.”  
  
Ren mewls, starting to thrust. The friction is absolutely maddening - it’s not nearly enough, but Ren’s soft stomach rubs across his length each time Ren ruts against his cock, and the sight of his little brother so lost in baseless pleasure has him finally breaching Ren’s entrance.

He hisses at the wetness clamping down around his fingers. Still so fucking tight.  
  
Goro makes quick work of fingering Ren open, probing at his inner walls, already able to reach so deep with his fingers only. Ren’s verbal output has been reduced to soft pants and needy sounds, and the sight of him squirming and writhing in his lap, spilling his small amounts of release against Goro’s cock already when Goro hits his prostate is gratifying beyond reasoning.  
  
" _Onii-chan_ ," Ren whines again. He's still now, recovering, letting Goro insert a second, a third finger with breathy whimpers only. "Gorooo-"  
  
He hushes him.

"I got you. Just a little longer. Be a good kitten for me."  
  
Because Ren really needs this preperation. Goro is far bigger than three fingers and Ren's already constricting so much around those digits only that Goro knows the breach will be painful for the both of them.  
  
But Ren is nothing more than perfect, already knows how to force his body to relax to accomodate the intrusion a little better. His little cock is hard again, dragging against Goro's, reminding him of his own need.  
  
Goro lets Ren scoot a little backwards when he carefully pulls his fingers out. He remains cross-legged, grabs the discarded lube, pours a generous amount of it directly onto his cock.

He shivers at the coolness of it, but the sight of Ren's pink tongue poking out to lick at his lips distracts him enough.  
  
"How do you want it, kitten?" Goro raspily asks, sliding his hands over Ren's body. So small, so warm, welcoming him, unraveling for him. "How do you want your big brother to take you?"

The response is immediate. "Use me," Ren pleads with little more than a whine. "Y-you can use me, onii-chan. I want to make you feel good."

"You always make me feel good," Goro responds, allowing a quick smile to fall onto his face, one that Ren tries his best to return.  
  
His sweet, little brother. Always eager to please, always the happiest when he's giving, when he sees that he makes other people happy.  
  
Well, not that there are many people to make happy in the first place - not anymore, Goro made sure of that.  
  
(Shido doesn't care for Ren either, something Goro is grateful for for once.)  
  
He'll have him dropping out of school soon to continue his education in private lessons, too - he can't take any risks, even if the bullying incidents were months ago.  
  
In this world, people as sweet as Ren will only get taken advantage of. But that's where his role as a big brother comes into play - to protect Ren from any harm possible.  
  
Goro smiles. "Come here."  
  
Ren quickly crawls over to him, making grabbing motions. Goro has no problem to pick him up, letting his wet entrance hover right above his cock.  
  
"Big brother won't be able to hold himself back," he warns, driving his thumbs over Ren's pink, little nubs once.

He revels in the needy sounds that follow. Perhaps he could start to train him to cum from his nipples only?

"You teased me enough already."

Ren only shakes his head, damp curls bouncing. And Goro grins haughtly, slowly lowering Ren him fown.

Ren is going to break.  
  
It won’t fit, Ren is molten pleasure, Goro will break him, Ren is tighter than a vice, it won’t fit.  
  
The darkest part of Goro _wants_ to see him break.  
  
To harshly drag him down, completely split him open oppsed to all of their preperation with a single push.  
  
But Goro holds himself back, groans loudly as Ren's walls constrict in rapid sessions, trying their best not accomodate the throbbing length.  
  
"Goro, _Goro_!!"  
  
"Shhh," Goro murmurs, leaning down to kiss Ren's tears away. They taste salty and sweet, and the taste melts on his tongue. "You're doing so well. Good kitten, good kitten."  
  
As always, Ren absolutely trashes in his hold. Whimpers and writhes, cries and squirms to the best of his ability.  
  
Goro barely feels it with his grip around Ren's waist, his small brother's trashing little more than a flies' buzz.

Inch by inch Goro slides in, his control so used up at the sensation of bliss encasing him that he can only go slow instead of stopping for breaks, and Ren's wide eyes roll back as soon as Goro bottoms out.  
  
Ren spasms the lightest bit, incoherent sounds filling the air alongside his grunts and strained intakes of breath.  
  
Goro sees the bulge.  
  
It’s obscene. The way it stretches Ren’s premature walls to the limit because of how deep Goro is, how a visible bump is jutting out, and the sight sets the rest of him loose.  
  
:Hold on," is all Goro says, and he laughs inwardly because he knows his little brother wont be able to.

But it's the only warning Ren gets before Goro lifts him easily, the act costing Goro a pitiful amount of energy with how light he is, and then slams him down.  
  
Goro moans, Ren whails in hurt and pleasure. He repeats the motion, beginning to fuck into him in earnest.  
  
It’s rapturous, a liquid fire running through his entire being, filling every space that previously remained hollow.

It's addictive, and Goro can only take, take, take what his little brother is so eager to give.  
  
But he's only abiding Ren's wishes by thoroughly using him, like Ren's his toy, a living, breathing fleshlight that clings tighter than any human.  
  
Goro barely moves his own hips, simply lets his arms and Ren's walls do most of the work.  
  
And Ren gets off on like the perfect, little brother he is, milking Goro's cock with every fiber of his being, like he's never done anything else.  
  
“ _Ahhh_!! G-Goro!!”  
  
Ren’s sweet cries grow louder with each thrust and how can Goro hold himself back like that, when his brother fits around him so perfectly like not a single other in the world, calling out his name?  
  
He picks up the pace, drills into him.  
  
"God, Ren. You’re made for this. Made for my cock, aren’t you?”

Ren's arm flail, trying to grab Goro's shoulders or wind around his torso. But Goro doesn't give him any chance to, keeps offsetting his balance with his pace and strength that Ren is unable to fight against with how much of a pliant, needy mess he is.  
  
“Onii-chan-”  
  
Goro can't get enough. Not of Ren, not of pulsating flesh curling around him endlessly with very lift and drop of his arms, not of the visual of Ren's stomach bulging everytime Goro drops him.

Goro doesn't know how many times Ren already came - he's grown so sensitive from all of their sessions and loses it quiet easily, cumming even when his cock isn't able to produce the proper amount of semen yet - because his little brother's head has rolled backwards, cocklet uselessly flopping in the air, unresponsive except from gurgles and broken sounds.  
  
Debauched, and truly his to use in every sense of the word.

"Perfect," Goro hisses, unable to do anything but devour more of the pleasure. "So fucking perfect."  
  
He thrusts three, four, five more times, bruises Ren's waist and hips and chest with how hard he's gripping, bruises his insides by the strength and size of his cock, and then lunges forward to sink his teeth into Ren's flushed, sweaty throat.   
  
Ren weakly cries in his arms as Goro fills him to the brim with his load. He suckles on Ren's skin, laps everything up, twitches even while cumming at the sight of Ren's stomach protruding just a little more with each heated second.  
  
Tremors wreck the weak body in his arms as Goro slowly pulls out, letting Ren sprawl limp across the mattress.

"Onii-chan-" Ren hiccups, so fucked out that he's unable to lift his head from his position on his back. "Onii-chan, ahh-"

Goro just came, but Ren's blotchy face, clumped eyelashes and the occasinal twitch of his limbs in combination with the sight of his cum leaking out of a gaping hole that can't properly close anymore sends all blood towards his groin.  
  
"Renren," he cooes, looming over the other to take every little detail in and commit it to memory.

He's going to fuck him again, then clean him up with his tongue. 

"My darling little brother."

**Author's Note:**

> i wrote this out of spite lol
> 
> happy valentines day?


End file.
